O boy time to replace the battery in my laptop.  

Hi, i have a Dell Latitude E6520 laptop and i am getting a message about my battery will charge fine but it may not last as long.  Well that might be expected sense when i got it i had to leave it plugged in for hours before the percentage started rising.  I am wanting to replace the battery in the laptop in the machine (preferably with the 9 cell) so it will last longer as i have noticed the battery life has gotten less.  Can someone provide me a link with one that won't break the bank?